ch 2 is matter around us pure Flashcards
what does a scientist mean when a substance is pure
When a scientist says that something is pure, it means that all the constituent particles of that substance are the same in their chemical
what is a mixture?
When two or more substances (elements, compounds or both) are physically mixed together in any proportion, such that they do not undergo any chemical change, but retain their individual characteristics, the resulting product is called a mixture.
what is a solution ?
solution is a homogeneous mixture of two or more substances.
define alloy
alloy are mixture of two or more metals or a metal and a non-metal is known as alloy. They can’t be separated to their original by physical methods.
for e.g. brass is made up of 30% zinc and 70% copper
what are the two parts of solution
solute and solvent
define solvent
The component of the solution
that dissolves the other component in it
(usually the component present in larger
amount) is called the solvent.
define solute
The component
of the solution that is dissolved in the solvent
(usually present in lesser quantity) is called
the solute.
what are the properties of a solution?
• A solution is a homogeneous mixture.
• The particles of a solution are smaller
than 1 nm (10^-9 metre) in diameter. So,
they cannot be seen by naked eyes.
• Because of very small particle size, they
do not scatter a beam of light passing
through the solution. So, the path of
light is not visible in a solution.
• The solute particles cannot be
separated from the mixture by the
process of filtration. The solute particles
do not settle down when left undisturbed,
that is, a solution is stable
what is a saturated solution?
a solution that has dissolved as much solute as it is
capable of dissolving, is said to be a saturated
solution. In other words, when no more solute
can be dissolved in a solution at a given
temperature, it is called a saturated solution
what is unsaturated solution?
If the amount of solute contained in a
solution is less than the saturation level, it is
called an unsaturated solution
what is the concentration of a solution?
The concentration of a solution is the amount
(mass or volume) of solute present in a given
amount (mass or volume) of solution
what’s the formula for finding the concentration of a solution by mass?
Mass by mass percentage of a solution
Mass of solute
———————– x 100
Mass of solution
what’s the formula for finding concentration of a solution by Mass and volume?
Mass by volume percentage of a solution
Mass of solute
—————————- x100
Volume of solution
what’s the formula for finding the concentration of a solution by volume?
Volume by volume percentage of a solution Volume of solute \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ x 100 Volume of solution
what kind of a mixture is a suspension?
A suspension is a heterogeneous mixture in which the solute particles do not dissolve but remain suspended throughout the bulk of the medium. Particles of a suspension are visible to the naked eye.
what are the properties of suspension ?
• Suspension is a heterogeneous
mixture.
• The particles of a suspension can be seen
by the naked eye.
• The particles of a suspension scatter a
beam of light passing through it and
make its path visible.
• The solute particles settle down when a
suspension is left undisturbed, that is,
a suspension is unstable. They can be
separated from the mixture by the
process of filtration. When the particles
settle down, the suspension breaks and
it does not scatter light any more.
what are the properties of a colloid ?
Properties of a colloid • A colloid is a heterogeneous mixture. • The size of particles of a colloid is too small to be individually seen by naked eyes. • Colloids are big enough to scatter a beam of light passing through it and make its path visible. • They do not settle down when left undisturbed, that is, a colloid is quite stable. • They cannot be separated from the mixture by the process of filtration. But, a special technique of separation known as centrifugation (perform activity 2.5), can be used to separate the colloidal particles
name the various ways heterogeneous mixtures can be separated?
Heterogeneous mixtures can be separated
into their respective constituents by simple
physical methods like handpicking, sieving,
filtration that we use in our day-to-day life.
Sometimes special techniques have to be used
for the separation of the components of a
mixture.
explain how centrifugation works
The principle
is that the denser particles are forced to the
bottom and the lighter particles stay at the
top when spun rapidly.
Give two examples of APPLICATIONS of centrifugation in real life
Applications • Used in diagnostic laboratories for blood and urine tests. • Used in dairies and home to separate butter from cream. • Used in washing machines to squeeze out water from wet clothes
how do immiscible liquids work?
The principle is that immiscible liquids
separate out in layers depending on their
densities.
what is chromatography?
This process of separation of components
of a mixture is known as chromatography.
Kroma in Greek means colour. This technique
was first used for separation of colours, so
this name was given. Chromatography is the
technique used for separation of those solutes
that dissolve in the same solvent.
give 2 applications if immiscible liquids
Applications • To separate mixture of oil and water. • In the extraction of iron from its ore, the lighter slag is removed from the top by this method to leave the molten iron at the bottom in the furnace.
give 2 real life examples of chromatography
Applications To separate • colours in a dye • pigments from natural colours • drugs from blood.
give reason how to separate 2 mixable liquids
for the separation of components of a mixture
containing two miscible liquids that boil
without decomposition and have sufficient
difference in their boiling points.
explain crystallization with example
Crystallisation is a
process that separates a pure solid in the form
of its crystals from a solution. Crystallisation
technique is better than simple evaporation
technique as –
• some solids decompose or some, like
sugar, may get charred on heating to
dryness.
• some impurities may remain dissolved
in the solution even after filtration. On
evaporation these contaminate the
solid.
Applications
• Purification of salt that we get from sea
water.
• Separation of crystals of alum (phitkari)
from impure samples.
what is a pure substance?
A homogeneous material which contains particles of only one kind and has a definite set of properties,is called a pure substance e.g. Oxygen, iron, sulphur etc.
What are the characteristics of a pure substance (mixture)?
Characteristics of pure substances
(1) A pure substance is homogeneous in nature.
(2) A pure substance has a definite set of properties.
(3) The composition of a pure substance cannot be altered by any physical means.
(4) A pure substance has a definite melting point, density, boiling point etc. For example, water is a pure substance because it has uniform composition throughout. It consists of only one kind of particles called water molecules, which cannot be separated into its constitue (H & O) by any simple physical process.
what are the characteristics of mixtures ?
Characteristics of mixtures
(1) A mixture may be homogeneous or heterogeneous.
(2) The constituents of a mixture can be separated by physical means like filtration, evaporation.sublimation and magnetic separation.
(3) In the preparation of a mixture energy is neither evolved nor absorbed.
(4) A mixture has no definite melting point and boiling point.
(5) The constituents of a mixture retain their original set of properties. For example, magnet attracts iron fillings in a mixture of sand and iron fillings.
what are the two types of pure substance ?
element and compound
explain the classification of mixtures ?
homogenous and heterogenous
